<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        /* 标签选择器 */
        p{
            color: red;
            font-weight: bold;
        }
        div{
            text-decoration: underline;
        }
        /* 类选择器 */
        .hello{
            background: pink;
            font-size: 30px;
        }
        .world{
            width: 400px;
            height: 100px;
        }
        .b2{
            font-style: italic;
        }
        /* ID选择器 */
        #welcome{
            background: blue;
        }
    </style>
</head>
<body>
    <!-- 通过id属性调用ID选择器 -->
    <p id="welcome">aaa</p>
    <div>bbb</div>
    <!-- 通过class属性调用类选择器 -->
    <p class="hello world">ccc</p>
    <span>ddd</span>
    <h2 class="hello b2">eee</h2>
    <p>fff</p>
</body>
</html>